Heating apparatus

ABSTRACT

The invention provides both a method and apparatus for heating a liquid. The apparatus incorporates a furnace chamber in which fuel, such as particulate coal, is burnt in a fluidized bed. The heat from the bed is transferred to the liquid contained in a jacket surrounding the furnace by transfer through the furnace casing, by transfer through conduits immersed in the bed and connected with the jacket through which conduits immersed in the bed and connected with the jacket through which conduits the liquid passes, and by transfer from exhaust gases of combustion fed through smoke tubes passing through the jacket. The liquid vapor produced by heating is drawn off the apparatus for use in further apparatus such as steam turbines.

Unite States Patent Inventors I Michael H. Barker [56] References Cited Surrey; UNITED STATES PATENTS filig'f gfi Lemherhead, Surrey 3,387,590 6/1968 Bishop 122 4 W Nu 821,778 2,997,286 8/1961 Fnese 122/4 X Filed May 5, 1969 Primary Examiner- Kenneth W. Sprague Patented June 29, 1971 Atl0rney--Stevens, Davis, Miller & Mosher Assignee Coal Industry Patents Limited London, England priority May 9, X968 ABSTRACT: The invent on provides both a method and ap- Great Britain paratus for heating a liquid. The apparatus incorporates a fur- 22067/68 nace chamber in which fuel, such as particulate coal, is burnt in a fluidized bed. The heat from the bed is transferred to the liquid contained in a jacket surrounding the furnace by transfer through the furnace casing, by transfer through conduits immersed in the bed and connected with the jacket g through which conduits immersed in the bed and connected US. Cl 122/4, with the jacket through which conduits the liquid passes, and 122/169 by transfer from exhaust gases of combustion fed through lnt.Cl F22b1/00 smoke tubes passing through the jacket. The liquid vapor Field of Search l22/4,4D, produced by heating is drawn off the apparatus for use in 169, 182 further apparatus such as steam turbines.

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sum u 0F 6 ==1. F 35 1 V1 33 VI IHIIEATIING APPARATUS This invention relates to a method of and apparatus for heating a liquid, as for example water for a boiler to raise steam.

It is known to heat a liquid by heat exchange with a fluidized bed of inert particles and finely divided fuel which is undergoing' combustion, the bed being maintained in the fluidized state by an upward flow of gas through the bed.

An object of the invention is to provide a method and apparatus which will operate at higher efficiencies than has hitherto been possible.

The invention provides a method of heating a liquid by heat exchange with a fluidized bed of inert particles and finely divided fuel, the bed being maintained in the fluidized state by an upward flow of gas through the bed, wherein the liquid to be heated is contained in a space located around the bed and said liquid is caused to flow through the bed from one location in said space to a different location in said space. Preferably the liquid flow path includes a linear portion inclined at an acute angle to the horizontal, e.g. -20.

Apparatus for carrying out the method of the invention comprises a furnace chamber having a lower part adapted, in use, to contain a bed of particulate material, a first inlet for admitting a gas to said part to fluidize the bed, and a second inlet for admitting fuel to said part, the furnace chamber being surrounded by ajacket adapted to contain a liquid to-be heated, tubes for the passage of liquid extending from one location in the jacket through the lower part of the furnace chamber to another location in the jacket so that liquid in the jacket can flow through the tubes and receive heat from the lower part of the furnace chamber.

Preferably the tubes within the furnace chamber and/or is suing from the chamber have a linear portion inclined at an acute angle to the horizontal, e.g. 520.

The invention is now described by way of example with reference to the accompanying drawings in which:

FIG. 1 is a vertical section ofa first embodiment on the line l-I in FIG. 3 but with parts repositioned for clarity;

FIG. 2 is a vertical section on the line II-II in FIG. 3;

FIG. 3 is a horizontal section on the line III-III in FIG. I with parts removed;

FIG. 4 is a vertical section through the second form of apparatus on the line IV-IV in FIG. 6;

FIG. 5 is a vertical elevation of part of the apparatus shown in FIG. 4 looking in the direction ofthe arrow in FIG. 4;

FIG. 6 is a horizontal section on the line VI-VI in FIG. 4;

FIG. 7 is a schematic view looking vertically downwards into the combustion chamber ofa third form of apparatus; and

FIG. 8 is a schematic section on the line VIII-VIII in FIG. 7.

FIGS. I, 2 and 3 show a water boiler comprising an outer casing I forming ajacket closed at the bottom by a flat disc 2 and at the top by a domed roof 3, and a furnace chamber 4 supported by a frustoconical mount 5 welded to the lower part ofa wall 6 of chamber I, and to the inside of easing I.

The wall 6 comprises a lower cylindrical portion 7 joined to a coaxial cylindrical exhaust portion 8 by a hollow frustoconical lower portion 9, and a domed roof It). The lower end of chamber 4 is closed by a horizontal gas-distributor plate II having perforations which may each have nonreturn devices (not shown) to prevent solid particles falling through. The plate 11 is supported on a hollow cylindrical member I2 formed at its lower end with an outwardly extending flange I3 secured to a similar flange I4 formed at the lower end of wall 6. A hollow cylindrical wind box registers with the member 12 beneath the plate 11. Air can be supplied to the wind box 15 through inlet conduit 16.

Inlet tube l7 for solid fuel, e.g. fine coal, leads into chamber 4, passing through holes formed in the outer casing of wind box 15 and plate 11, and terminating at its upper end in a T- piece I8 situated just above the upper surface of plate 11, the arms of the T" extending horizontally and having open ends.

A hole formed in the frustoconical portion 9 of the furnace chamber wall and leading to a downwardly sloping discharge conduit 19 forms a weir, which keeps constant the level of a fluidized bed in the lower portion ofchamber 4.

Tubes 20 pass through a lower part of the furnace chamber wall 6 and extend at each end a short distance beyond the wall. The tubes 20 are open at each end and parallel to one another, and are arranged in four rows, one above the other. The axes of the tubes 20 in each row lie in a plane inclined to thehorizontal at an angle of approximately 10 although any angle between 5 and 20 may be conveniently used, and the tubes in each row are so spaced that the axes of adjacent tubes in that row are separated by a distance equal to twice the external diameter of each tube. The tubes 20 of adjacent rows are laterally displaced so that the vertical planes containing the axes of the tubes each contain only the axes of tubes in alternate rows and the vertical planes are equally spaced from one another. The plane containing the axes of the tubes 20 in each row is spaced in a vertical direction from the plane containing the axes of the tube in the or each adjacent row by a distance approximately equal to the external diameter of a tube.

Exhaust gases leave the furnace chamber 4 through smoke exhaust tubes 21, which are coiled around the furnace chamber and lead from holes in the upper portion 8 of the furnace chamber wall to holes in the mount 5. The gases leave mount 5 through an aperture 26.

The apparatus operates as follows. Water is supplied to the jacket formed between the outer casing I and the furnace chamber wall 6, to a depth sufficient to submerge completely the roof 10 of chamber 4. A bed of inert particles e.g. crushed firebrick of maximum diameter of about oneeighth inch is placed in the chamber 4, and air under pressure is fed through inlet conduit 16 into wind box 15 and through distributor plate 11 upwardly through the bed. The rate of supply of air is ad justed to fluidize the bed of particles, and a controlled quantity of fine coal having a maximum particle diameter of onefourth inch is pneumatically supplied to chamber 4 through tube 17. Three pilot gas burners (not shown) are used to ignite the coal.

The rate of supply of coal is such that the coal forms only a small proportion of the contents of the bed by weight.

The bulk (generally of the order of percent by weight) of the ash formed is in the form of small particles which are carried off with the exhaust gases and the remainder is in the form of larger particles which are retained until reduced by abrasion.

The level of the bed above tubes 20 is kept constant by a sloping conduit I9 down which particulate material falls, the material being removed from the sloping conduit periodically.

The heat developed by the furnace chamber 4 is transferred to water which enters the tubes 20 at their lowest ends and flows through them under the action of convection. During the course of its passage through the tubes 20, the water boils and the presence of steam bubbles in the water tends to increase the velocity of flow of fluid through the tubes. The hot exhaust gases which leave the furnace chamber through the helical smoke tubes 21 also lose heat to the water. Typically, the gases leave the furnace chamber at a temperature of approximately 800 C, and pass along the smoke tubes 21 which are surrounded by water, and leave the tubes at a temperature of approximately 250 C. The water temperature is approximately l60 C.

The steam generated leaves the boiler through a valve 22. The water lost from the boiler in the form of steam is replaced by water supplied through a valve and a tube 23 supported on the roof 10 of the furnace chamber 4 and having a closed end 24 and a perforated wall 25.

The second form of apparatus shown in FIGS. 4, S and 6 is basically similar to the first, but the: arrangement of smoke tubes is different and the shape of the furnace chamber and outer casing are also different.

The apparatus consists of an outer casing 27 having a cylindrical wall 28, the top and bottom of which are not shown. The casing 27 contains a furnace chamber 29, the wall 30 of which is supported by a circular mount 31 joined to the inside of the casing 27 and to the lower end of the wall 30 of the furnace chamber 29. The walls of the casing 27 above the furnace chamber 29 are bounded by a circular plate 32.

The wall 30 of the furnace chamber 29 consists of two cylindrical portions, the upper portion 33 being of greater diameter and being closed at the top of a flat disc 35, and at the bottom by a flat disc 36, which has an offcenter hole. The lower portion 34 registers with the hole 36 in the disc 35. As in the first form of apparatus, the furnace chamber 29 has, close to its lower end, a conventional distributor plate surmounting a wind box and a coal inlet pipe, these features not being shown in FIGS. 4 to 6.

Tubes 37 pass through the lower portion of the furnace chamber wall 30 and are arranged in a similar way to the tubes in FIGS. 1-3.

Exhaust gases leave chamber 29 through three sets of straight, vertical smoke tubes 38, 40 and 41. Tubes 38 communicate' between the circular mount 31 and the annular region 39, i.e. the region of the flat disc 36 outside the hole which communicates with the lower portion 34 of the furnace chamber wall. The axes of the tubes 38 are approximately evenly spaced, and the tubes are arranged in a crescent formation centered on the widest part of the annular region, the center of the crescent formation being left free of tubes.

At their lower ends, the tubes 38 communicate via conventional smoke boxes with a second set of tubes 40 which, as seen in FIG. 6 are arranged in two arcuate series about the furnace chamber 29, each series being two tubes deep. The tubes 40 communicate between holes in the tubes mount 31 and holes in the circular plate 32. At their upper ends, the tubes 40 communicate with a third set of tubes 41, via conventional smoke boxes (not shown) and the tubes 41 lead from holes in the circular plate 32 at their upper ends to holes in the circular mount 31 at their lower ends. The tubes 41 are arranged in two arcuate series, each arc being two tubes deep, the arcs of tubes 40 and 41 being arranged so that the spaces between the arcs are aligned with the similar spaces between the groups of tubes 38.

The manner of operation of the second form of apparatus is essentially similar to that of the first.

In a further modification, shown schematically in FIGS. 7 and 8, the tubes 20 may be replaced by tubes 60 each of approximate U-shape and each having central upright portions joining inclined radial portions. Two such tubes may occupy a common radial plane, as shown. Water or other fluid enters at the lower end of each tube as before.

Although the invention has been described in relation to the heating of water, or the raising of steam, it is applicable wherever a fluid is required to be heated or converted to its vapor form.

Although convection circulation of fluid through the furnace chamber has been described, the invention includes the use of pumped circulation also. instead of solid fuel, liquid or gaseous fuel may be used; in this case the fluidized bed may consist wholly of inert particles.

We claim:

1. Apparatus for heating a liquid comprising a furnace chamber having a lower part adapted, in use, to contain a bed of particulate material, a first inlet for admitting a gas to said part to fluidize the bed, and an inlet for admitting fuel to said part, a jacket surrounding the furnace chamber, the jacket being adapted to contain a liquid to be heated, tubes for the passage of liquid extending from one location in the jacket through the lower part of the furnace chamber to another location in the jacket so that liquid in the jacket can flow through the tubes and receive heat from the lower part of the furnace chamber, exhaust means for removing the gases of combustion from the furnace chamber including exhaust tubes connected to an upper exhaust portion to receive gases of combustion, the exhaust tubes extending outside the furnace chamber into the jacket and outlet means for the liquid vapors,

2. Apparatus according to claim 1 wherein at least some of the tube lengths within the furnace chamber and/0r issuing from the chamber are linear and are inclined at an acute angle to the horizontal.

3. Apparatus according to claim 2, wherein the angle of inclination is between 5 and 20.

4. Apparatus according to claim 2 wherein the tube lengths within the furnace chamber are of approximately U-shape.

5. Apparatus according to claim 1 wherein the furnace chamber in contained within an outer casing adapted to contain the liquid to be heated at a level above the top of the furnace chamber.

6. Apparatus according to claim 1, including a preheating member adjacent the first inlet, the preheating member being connected to the exhaust tubes in order to enable fluidizing gas to be preheated.

7. Apparatus according to claim 1 comprising a discharge outlet positioned within the furnace chamber for maintaining the level to the bed constant.

8. In apparatus for heating a liquid comprising a furnace chamber having a lower part containing a bed of particulate material and fuel in a fluidized and combusting state, a first inlet admitting a gas to the bed, and inlet admitting fuel to the bed; and an upper part receiving the gases of combustion from the bed, exhaust tubes connected with the said upper part and conducting the gases of combustion away from the upper part; a casing surrounding the furnace chamber and forming a jacket between the furnace chamber and the casing, liquid in the jacket completely covering the furnace chamber, tubes in the furnace chamber passing through the fluidized bed, the liquid passing through the tubes and receiving heat from the bed, the tubes having a linear part inclined to the horizontal; the exhaust tubes passing through the liquid and the gases in the tubes heating the liquid, and an outlet in the casing through which vapors of the liquid produced by heating are drawn off.

9. A method of heating a liquid by heat exchange with a fluidized bed of particulate material comprising the steps of introducing an upward flow of gas through the bed whereby the bed is maintained in a fluidized state, introducing finely divided fuel into the fluidized bed, burning the fuel in a fluidized state within the bed, arranging the liquid in a space located around the bed, causing the liquid to flow from one location in said space through said bed to a different location in said space whereby the liquid receives heat from the bed and conducting the exhausted gases through the liquid in said space in heat exchange relationship with the liquid.

10. A method according to claim 9, wherein the path of the liquid through the bed includes a linear portion inclined to an acute angle to the horizontal.

11. A method according to claim 10, wherein the acute angle is between 5 and 20 12. A method according to claim 9, wherein the bed and the region above the bed containing the gases of combustion are completely surrounded by the liquid. 

1. Apparatus for heating a liquid comprising a furnace chamber having a lower part adapted, in use, to contain a bed of particulate material, a first inlet for admitting a gas to said part to fluidize the bed, and an inlet for admitting fuel to said part, a jacket surrounding the furnace chamber, the jacket being adapted to contain a liquid to be heated, tubes for the passage of liquid extending from one location in the jacket through the lower part of the furnace chamber to another location in the jacket so that liquid in the jacket can flow through the tubes and receive heat from the lower part of the furnace chamber, exhaust means for removing the gases of combustion from the furnace chamber including exhaust tubes connected to an upper exhaust portion to receive gases of combustion, the exhaust tubes extending outside the furnace chamber into the jacket and outlet means for the liquid vapors.
 2. Apparatus according to claim 1 wherein at least some of the tube lengths within the furnace chamber and/or issuing from the chamber are linear and are inclined at an acute angle to the horizontal.
 3. Apparatus according to claim 2, wherein the angle of inclination is between 5* and 20* .
 4. Apparatus according to claim 2 wherein the tube lengths within the furnace chamber are of approximately U-shape.
 5. Apparatus according to claim 1 wherein the furnace chamber in contained within an outer casing adapted to contain the liquid to be heated at a level above the top of the furnace chamber.
 6. Apparatus according to claim 1, including a preheating member adjacent the first inlet, the preheating member being connected to the exhaust tubes in order to enable fluidizing gas to be preheated.
 7. Apparatus according to claim 1 comprising a discharge outlet positioned within the furnace chamber for maintaining the level to the bed constant.
 8. In apparatus for heating a liquid comprising a furnace chamber having a lower part containing a bed of particulate material and fuel in a fluidized and combusting state, a first inlet admitting a gas to the bed, and inlet admitting fuel to the bed; and an upper part receiving the gases of combustion from the bed, exhaust tubes connected with the said upper part and conducting the gases of combustion away from the upper part; a casing surrounding the furnace chamber and forming a jacket between the furnace chamber and the casing, liquid in the jacket completely covering the furnace chamber, tubes in the furnace chamber passing through the fluidized bed, the liquid passing through the tubes and receiving heat from the bed, the tubes having a linear part inclined to the horizontal; the exhaust tubes passing through the liquid and the gases in the tubes heating the liquid, and an outlet in the casing through which vapors of the liquid produced by heating are drawn off.
 9. A method of heating a liquid by heat exchange with a fluidized bed of particulate material comprising the steps of introducing an upward flow of gas through the bed whereby the bed is maintained in a fluidized state, introducing finely divided fuel into the fluidized bed, burNing the fuel in a fluidized state within the bed, arranging the liquid in a space located around the bed, causing the liquid to flow from one location in said space through said bed to a different location in said space whereby the liquid receives heat from the bed and conducting the exhausted gases through the liquid in said space in heat exchange relationship with the liquid.
 10. A method according to claim 9, wherein the path of the liquid through the bed includes a linear portion inclined to an acute angle to the horizontal.
 11. A method according to claim 10, wherein the acute angle is between 5* and 20* .
 12. A method according to claim 9, wherein the bed and the region above the bed containing the gases of combustion are completely surrounded by the liquid. 